The architectural and functional group complexity of natural products often confers to them unique modes of biological activity and significant therapeutic value. Despite transformative advances in catalytic methods and strategies for constructing highly complex molecules, the practice of total synthesis still remains a laborious and time intensive pursuit. Consequently, such compounds are rarely sought or evaluated as potential therapeutics. Historically, the development of new synthetic methods has had a profound impact on the efficiency of complex molecule synthesis. New reaction classes that lead to fundamentally novel reactivity stand to promote the largest advances in this regard. As a guide, we can look towards Nature?s synthetic strategies that systematically employ C-H oxidation and complexity generating C-C bond forming reactions. This proposal seeks to establish allylic C-H bonds as a new functional group for widespread use in complex molecule synthesis. To achieve this goal we will exploit a highly versatile ?-allyPd intermediate, accessed through allylic C-H cleavage, and develop general strategies by which it can participate in diverse reaction types with consistently high selectivities. Collectively, we expect these Pd(II)-catalyzed allylic C-H functionalization reactions to become fundamental tools for streamlining the synthesis of important structural motifs found in natural products, bioactive compounds, and medicinal agents. Moreover, the general principles that emerge from this approach will be broadly applicable to the field of C-H activation.)